Technical Study On Continuous Preparation Of EGCG And ECG By Simulated Moving Bed

Simulated moving bed chromatography, developed from 1960s, is a kind of continuous preparative chromatography with many advantages, such as improving product purity and recovery, increasing the separation efficiency and reducing costs and so on. In this study, a simulated moving bed with four columns and three zones was designed and assembled, and 98% tea polyphenol(more than 20% ECG and 50% EGCG) and 70% EGCG were separated by traditional simulated moving bed process, Varicol process and Partial-discard process. Based on mobile phase and elution flowrate determined by single column chromatography, influencing factors in separation results, such as switching time, column configuration, feed flowrate, flushing flowrate and discarding time of Partial-discard process were optimized. Therefore, the optimal parameters of continuously preparing of EGCG and ECG were obtained. Besides, merits and demerits of three processes were compared in this study. The main results were as follows:1. SMB had higher separation efficiency, lower stationary phase and mobile phase consumption and lower cost than single column chromatography. Compared with 1/2/1 column configuration of four-column three-zone SMB, 1/1/2 colum configuration was more favorable for purifying weak retention component. With regard to separating low purity mixtures, Varicol process and Partial-discard process had an advantage over traditional SMB process. Varicol process had the advantages of high purity and recovery, and Partial-discard process had the advantages of increasing the concentration of raffinate and the purity of products.2. With C₁₈ bonded silica gel as stationary phase, ethanol and water (20︰80, V/V) as mobile phase, TP98 was separated by Varicol process. Switching period was 18 min, and was divided into two subinterval, i.e., 10 min at 1/2/1 column configuration at first; then 8 min at 1/1/2 column configuration. Feed concentration, feed flowrate, elution flowrate and flushing flowrate was fixed at 0.1 g/mL, 0.15 mL/min, 1.2 mL/min and 2.5 mL/min respectively. In this condition, ECG was obtained with 91.33% purity, 91.41% recovery and 21.26% yield.3. Partial-discard process at 1/1/2 column configuration was employed to separate TP98 to get EGCG. Collection of raffinate for 8 min was discarded at the beginning of switching period, and the later raffinate for 10 min was collected during the 18 min switching period. Feed concentration, feed flowrate, elution flowrate and flushing flowrate was fixed at 0.1 g/mL, 0.15 mL/min, 1.2 mL/min and 2.5 mL/min respectively. In this condition, EGCG was obtained with 90.12% purity, 97.83% recovery and 61.21% yield.4. EGCG70 was separated by traditional SMB process at 1/1/2 column configuration to get EGCG. Switching period, feed concentration, feed flowrate, elution flowrate and flushing flowrate was fixed at 15 min, 0.1 g/mL, 0.15 mL/min, 1.2 mL/min and 2.5 mL/min respectively. In this condition, EGCG was obtained with 95.17% purity, 96.21% recovery and 72.16% yield.